1. Field of the Invention
The present invention relates to a sewing movement control method and a contour sewing machine, particularly relates to a sewing movement control method and a contour sewing machine in which sewing holding means for holding sewing can be moved along the surface of a bed so that predetermined contour sewing is executed.
2. Description of the Related Art
Heretofore, a contour sewing machine for executing predetermined contour sewing for sewing is known. Such a contour sewing machine is constituted so that sewing holding means for holding sewing by the driving force of a pair of driving motors respectively composed of a pulse motor arranged in the lower part of a bed with its output shaft perpendicular to the bed and also called a stepping motor and others is moved at rectangular coordinates (the X-Y coordinates) in longitudinal and transverse two directions (XY directions) mutually perpendicular, which is called XY driving.
Recently, a contour sewing machine in which sewing holding means can be moved in longitudinal and transverse two different directions approximately perpendicular by converting the operation of one of a pair of driving motors to approximate linear motion so-called circular arc motion, converting the operation of the other to approximate linear motion or linear motion and moving the sewing holding means curvedly such as in a circular arc approximating to a straight line in at least one direction for the reason of miniaturization and others is known.
For a contour sewing machine in which sewing holding means is moved in longitudinal and transverse two directions approximately perpendicular along the surface of a bed by converting both driving force of a pair of driving motors to approximate linear motion called circular arc motion, the following are known.
For example, in U.S. Pat. No. 4,455,956, a contour sewing machine provided with a pair of driving motors respectively composed of a pulse motor arranged in the lower part of a bed with its output shaft perpendicular to the bed, a pair of sectorial spur gears for being engaged with a pinion gear fixed to the output shaft of each driving motor, a series of a group of levers for approximately moving sewing holding means in one direction (in the direction of the y-axis, that is, longitudinally) along the surface of a bed according to the reciprocation of one sectorial spur gear and a series of a group of levers for approximately moving the sewing holding means in the other direction (in the direction of the x-axis, that is, transversely) along the surface of the bed according to the reciprocation of the other sectorial spur gear is disclosed.
Further, for another example, in Japanese published unexamined patent application No. Hei8-84877, a contour sewing machine provided with a pair of driving motors arranged in the lower part of a bed with its output shaft level with the bed, helical engagement means coaxially fixed to the output shaft of each driving motor, an engagement piece which is engaged with the helical engagement means and can be moved in the axial direction of the output shaft of the driving motor, a series of a group of levers for reciprocating the movement in the axial direction of one engagement piece by a linear lever and approximately moving sewing holding means in one direction (in the direction of the y-axis, that is, longitudinally) along the surface of the bed, a series of a group of levers for reciprocating the movement in the axial direction of the other engagement piece by a L-type lever and approximately moving the sewing holding means in the other direction (in the direction of the x-axis, that is, transversely) along the surface of the bed is disclosed.
In the above each contour sewing machine, the data of the driven quantity (the number of pulses) of the pulse motor which is the driving motor for moving the sewing holding means by linear driving or driving in a circular arc which is approximate linear motion is collected as sewing data for contour sewing and stored in data storage means such as programmable ROM (PROM) and in case contour sewing is executed, the integral times (resolution in data/the resolution of pulse motors) of the sewing data is output.
However, in the above conventional type contour sewing machines in which at least one of different directions is driving in a circular arc, as the sewing holding means is moved in a circular arc which is at least one of different directions, there is a problem that a position from a home position to which the sewing holding means is moved cannot be precisely controlled only by simply enlarging or reducing sewing data, so-called distortion of a contour is caused and if particularly, a sewing area is large, the distortion of a contour is increased.
In the contour sewing machines of the related art, there is another problem that different sewing data is required because of difference between methods (XY driving and driving in a circular arc) of moving the sewing holding means by a pair of driving motors and much labor and time are required to generate sewing data.
Further, in the above related contour sewing machines wherein at least one of directions in which the sewing holding means is moved is driving in a circular arc, quantity in which the sewing holding means is moved may be different depending upon the resolution of each pulse motor and in such a case, there is a problem that dedicated sewing data is required and more labor and time are required to generate sewing data.
Furthermore, in a contour sewing machine wherein a sewing pattern in which a sewing contour is recorded is stored in sewing holding means and sewing data can be input by moving the sewing holding means according to the sewing pattern, there is a problem that only in a contour sewing machine to which sewing data is input, can the sewing data can be generated and used.
That is, in a related contour sewing machine, there is a problem that sewing data cannot be shared because of difference in a driving method and in a sewing area.